#include<bits/stdc++.h>
using namespace std;
#define fi first
#define se second
#define pb push_back
#define mpr make_pair
#define db double
#define ll long long

const int maxn=1e2+10;
int n;
string s[maxn];
int a[maxn],b[maxn],k[maxn];
void calc(int a,int b,int c,int d,int e,int f,int&x,int&y){
    ll U=1ll*a*f-1ll*c*d;
    ll D=1ll*e*c-1ll*b*f;
    if(U%D){
        x=-1,y=-1;
        return;
    }
    x=U/D;
    if(x<=0){
        x=-1,y=-1;
        return;
    }
    U=a+1ll*b*x;
    D=c;
    if(U%D){
        x=-1;
        y=-1;
        return;
    }
    y=U/D;
    if(y<=0){
        x=y=-1;
        return;
    }
    return;
}
void solve(){
    cin>>n;
    int sta=0;
    for(int i=1;i<=n;i++){
        cin>>s[i];
        if(s[i].back()=='{')k[i]=sta++;
        else if(s[i].back()=='}')k[i]=--sta;
        else assert(0);
        for(int j=0;j+1<s[i].size();j++){
            if(s[i][j]=='s')a[i]++;
            else assert(s[i][j]=='t'),b[i]++;
        }
        if(!(a[i]+b[i]+k[i]))continue;
        int g=__gcd(a[i],__gcd(b[i],k[i]));
        a[i]/=g;
        b[i]/=g;
        k[i]/=g;

    }
    if(n==2){
        cout<<1<<"\n";
        return;
    }
    int aa=a[2],bb=b[2],cc=k[2];
    int t=0,w=0;
    for(int i=3;i<n;i++){
        int d=a[i],e=b[i],f=k[i];
        if(1ll*e*cc==1ll*bb*f){
            if(1ll*aa*e==1ll*bb*d)continue;
            else return cout<<"-1\n",void();
        }
        else{
            calc(aa,bb,cc,d,e,f,t,w);
            if(t==-1){
                cout<<-1<<"\n";
                return;
            }
            else break;
        }
    }
    for(int i=1;i<=n;i++){
        if(a[i]+b[i]*t!=k[i]*w){
            cout<<-1<<"\n";
            return;
        }
    }
    cout<<t<<"\n";
    return;
}
signed main(){
    ios::sync_with_stdio(0);
    cin.tie(0),cout.tie(0);
    int t=1;
    // cin>>t;
    while(t--){
        solve();
    }
    return 0;
}